(i) Field of the invention
The present invention relates to manual countershaft transmissions that are used in road and off-road vehicles, machinery, and other drive applications where there is a need to alter either the torque or the speed of the output from a prime mover.
(ii) Description of the Prior Art
The structures of present manual countershaft transmissions incorporate one gear-pair for each selectable ratio, with the gear-pairs selected independently either in or out of continuum. This method of selecting the ratio changes in countershaft transmissions requires a large number of gear-pairs and relatively complex selecter mechanisms when more than five ratios are required.
The following patents reflect the state-of-the-art techniques used to select the ratios in present manual countershaft transmissions:
U.S. Pat. No. 2,019,923 "Change Speed Gearing" Molly-Patented Nov. 5, 1935. PA1 Can Pat. No. 720,214 "Gear Changing Mechanism" Gronau-Oct. 26, 1965. PA1 U.S. Pat. No. 3,273,413 "Transmission with Automatic Meshing Control" Stobbe & Zankl-Patented Sept. 20, 1966. PA1 Can. No. Pat. 1,038,202 "Variable Ratio Gear Transmission" Keller-Sept. 12, 1978. PA1 Can Pat. No. 696,915 "Geometrically Progressive Gear Box" Feuillastre Feb. 6, 1960. PA1 U.S. Pat. No. 3,491,862 "Transmission Ratio Control For A Tractor Drivetrain" Tanzer-Patented Jan. 27, 1970.